1. Field of the Invention
The present invention relates to a luminous element which can be used for, for example, a display device. More particularly, this invention relates to a proposal of a new luminous element which uses a material capable of emitting light upon sensing pressure.
2. Description of Related Art
As various energies are applied to a substance, electrons in the substance transit from the ground state to the excited state and then return to the ground state, and the substance sometimes emits light. This is generally called a luminescence phenomenon. It has been confirmed that specific substances exhibit a tribo-luminescence phenomenon in which they emit light upon the application of friction or pressure.
For example, a treatise of R. Nowak et al. entitled "Efficient Triboluminescence in N-isopropylcarbazole" (Chemical Physics Letters, Vol. 94, No. 3, 21/01/1983) describes that when pressure is applied to crystals of N-isopropylcarbazole, the crystals emit blue light of wavelengths of 400 nm to 500 nm. Moreover, a treatise of A. J. Smiel entitled "Triboluminescence of Silica Core Optical Fibers" (Appl. Phys. Lett. 40(2), 15/01/1982) and a treatise entitled "Broadband Triboluminescence in Silica Core Fiber Optic Waveguides" (Appl. Phys. Lett. 41(4), 15/08/1982) describe that amorphous glass of SiO.sub.2 emits blue, red, or white light. Also, a treatise of Takada et al. entitled "Transient Behaviour of Mechanoluminescence from Europium Complex in Powder and in Polymer-Dispersed Film" (UPS-8, 1997) describes that a substance called Eu(TTA).sub.3 emits red light. Furthermore, a treatise of J. I. Zink entitled "Accounts of Chemical Research" (Vol. 11, No. 8, 08/1978, p.p. 289-295) and a treatise of Linda M. Sweeting et al. entitled "Crystal Structure and Triboluminescence 2. 9-Anthrancenecarboxylic Acid and Its Esters" (Chem. Mater. Vol. 9, No. 5, 1997, p.p. 1103-1115) describe a substance that exhibits a tribo-luminescence phenomenon.
Although research has been conducted on this tribo-luminescence phenomenon, the commercialization of such a phenomenon has not been realized.